Engine cylinder scavenging



Nov. 1955 c. H. SCHOWALTER 2,724,372

ENGINE CYLINDER SCAVENGING Filed Aug. 5, 1952 5 Sheets-Sheet 1 INVENTOR(Zara-m A! diwmzrm EAL a M ATTY.

c. H. SCHOWALTER 2,724,372

ENGINE CYLINDER SCAVENGING 5 Sheets-Sheet 2 Nov. 22, 1955 Filed Aug. 5,1952 INVENTOR. Cue-fives A! dawn 4L fi A TTYI w mv NW. 4mm. \Mm

C. H. SCHOWALTER ENGINE CYLINDER SCAVENGING Nov. 22, 1955 5 Sheets-Sheet3 Filed Aug. 5, 1952 INVEN'I'OR. C(MEms b. \S'CIIOMMrEK Nov. 22, 1955 c.H. SCHOWALTER ENGINE CYLINDER SCAVENGING 5 Sheets-Sheet 4 Filed Aug. 5,1952 mmmg U 33G @cr ATTIC BY @Lx. n.1,,

C. H. SCHOWALTER ENG NE CYLINDER SCAVENGING Nov. 22, 1955 Filed Aug INVEN TOR. Cims/mc f7. dcflaumrm ATTK United States Patent Office2,724,372 Patented Nov. 22, 1955 ENGINE CYLINDER SCAVENGING Clarence H.Schowalter, Beloit, Wis., assignor to Fair banks, Morse & Co., Chicago,11]., a corporatlon of Illinois Application August 5, 1952, Serial No.302,765

11 Claims. (Cl. 123-65) This invention relates to improvements ininternal combustion engines, and more particularly to improvements incylinder scavenging and cylinder admission of combustion air in enginesof two cycle, high compression type suitable for operation on liquidfuel, as a Diesel engine, or on gaseous fuel with ignition thereofeffected fuel-air mixture. Since in two cycle engines of this character,efiiciency and power output are directly dependent in large part, uponthe character and uniformity of gas and air mixtures in combustion andthe effectiveness and extent of cylinder scavenging, relatively closecontrol of the latter factors is highly important and essential to goodengine operation. Comparatively speaking, the, degree of control of theaforementioned factors is considerably more exacting for properoperation of gaseous fuel engines of the character indicated, thanisrequired for effective operation of conventional two cycle Dieselengines.

Accordingly, it is an object of the present invention to provide animproved arrangement ofcylinder intake and exhaust porting for a twocycle, high compression engine having the intake and exhaust ports inthecylinder wall and piston controlled, wherein the form and relativearrangement of the ports are such as to afford a markedly improvedcylinder scavenging of exhaust gases and products of combustion withoutby-pass of scavenging air to the exhaust ports, and to effect supply ofair in proper volume for combustion mixture with the gaseous fuel in thecylinder, with the combustion air admitted to the cylinder such as toavoid gas stratification and the formation of cylinder pockets ofrelatively rich gas-air mixtures. Prevention of localized zones orpockets of rich gas-air mixtures in the cylinder is highly important aswill be fully appreciated, as otherwise auto-ignition of such richmixtures would occur in the compression period, with resultantdetonation of the cylinder charge and consequent reduction in enginepower output.

Another object is to provide, for an engine of the character indicated,cylinder intake and exhaust ports of such improved form and relativearrangement as to result in amore effective directional flow ofscavenging air in the cylinder for assuring substantially completecylinder scavenging, as well as a more rapid exhaust discharge orcylinder exhaust blow-down through quick development of an adequatelylarge exhaust port area, the port arrangement further being adaptedpartly through valve control of certain of the intake ports, forproviding relatively high mean effective scavenging and air chargingpressures in the cylinder.

A further object is to afford in an engine of the character indicated,an improved system of air intake and exhaust ports providing the severaladvantages hereinbefore objectively stated, and affording effectivecylinder scavenging in such efficient manner as to enable an appreciablereduction in the volume of air required, thereby reducing bloweroperating power requirements while increasing the net power output ofthe engine.

The foregoing and other objects and advantages of the present inventionwill appear from the following description of embodiments thereofillustrated by the accompanying drawings, wherein:

Fig. l is a vertical transverse section through a cylinder assembly ofan engine shown partly in elevation, showing the cylinder having exhaustand air ports according to the present invention.

Fig. 2 is an enlarged, horizontal section through a cylinder, as takenalong line 2-2 in Fig. 1.

Fig. 3 is a similar enlarged, horizontal section through the cylinder,as viewed from line 3-3 in Fig. 1.

Fig. 4 is a developed view of the air intake and exhaust ports of thecylinder.

Fig. 5 is a developed view of a modified arrangement of exhaust and airports.

Fig. 6 is a vertical section through an exhaust port, as taken alongline 6-6 in Fig. 2.

Fig. 7 is a vertical section transversely of the cylinder wall in a zoneof an air port and an exhaust port thereabove, as taken in a verticalplane along line 7-7 in Fig. 8 is a vertical section transversely of thecylinder wall in a zone of superposed air ports, as taken in a verticalplane along line 8-8 in Fig. 3.

Fig. 9 is a vertical section transversely of the cylinder wall in a zonethereof containing one air port, the View being along line 9-9 in Fig.2.

Referring first to Fig. 1, the view illustrates in vertical section, acylinder and piston assembly of a high compression internal combustionengine of two-cycle type which may be adapted for dual-fuel operation,as alternatively on liquid fuel alone or on gaseous fuel ignited insuitable manner, as by a pilot charge of liquid fuel. Since the improvedcylinder port arrangement of the present invention is directedparticularly to obtaining eflicient operation of the engine on gaseousfuel, the following description of the port system will be presented inrespect to gas operation of the engine.

The engine as shown, provides a frame structure generally designated bythe numeral 10, supporting one or more cylinder organizations only oneof which is illustrated as including a cylinder 11 and cylinder headmember 12 forming combustion chamber 14 extending into the cylinder headas at 15. Operative in the cylinder is a suitable piston 16 having afrusto-conical crown l8 (later to be referred to), the piston beingconnected to the engine crankshaft (not shown) through connecting rod19. Carried by the cylinder head member are a valve device 20 ofsuitable character for controlling cylinder admission of gaseous fuel,and liquid fuel admission means such as valve 22. Valve 20 may beengine-actuated through a rocker arm 23 to determine gas valve openingat the proper time in the fuel admission-compression cycle of the engineduring engine operation on gas fuel, while for diesel operation of theengine, liquid fuel is pumped by suitable fuel injection pump means notshown, to the Valve means 22 for cylinder injection. In gas operation ofthe engine, the gas-air mixture is ignited by any suitable, desiredignition means which for example, may be a predetermined small volume orpilot charge of liquid fuel injected into the cylinder, as through valve22 for instance, and cornpression-ignited therein. The gas ignitionmeans is not here shown, since it does not form any material part of thepresent invention.

The cylinder 11 preferably is of double-walled construction to provide ajacket space 26 for cooling fluid, and is formed to provide a pluralityof exhaust port passages 27 in communication with a discharge chamber 28in the engine frame, the latter opening to an exhaust discharge manifoldgenerally indicated at 3h. The cylinder further provides upper and lowerrows of air port passages 31 and 32 respectively, the lower row openingto the air space 34 between the cylinder and frame, while the upper row31 is divided shown by Fig. 3, with the division separately suppliedwith air through air delivery passages 35 in the frame (Fig. 3). An airconduit or distribution manifold as delivers air under a suitable,predetermined pressure, to the space 34 for cylinder admission throughport passages 32., and to the separate passages 35 throughunidirectional air valve devices 38 of any suitable construction, forcylinder delivery by the port passages 31. Such scavenging and chargingair supply in the manifold 36, may be established in usual manner, as bysuitable blower means (not shown) which may be either engine-driven oroperated by separate power means as an electric motor or the like.

Referring particularly to Fig. 2, the air port passages 32 of the lowerrow are distributed in circumferentially spaced relation on oppositesides of a median longitudinal plane AA through the cylinder center, andover somewhat more than half the cylinder circumference. In the exampleillustrated, the circumferential extent of passage distributionapproaches approximately two-thirds of the cylinder circumference, Whilethe passage. distribution preferably is symmetrical with respectto themedian plane. The passages 32, terminate in air intake openings or airports 40, and each passage is inclined in the cylinder wall (Figs. 7, 8,and 9) toward the outer or head end 41 of the cylinder (Fig. 1).According to the present example, five such passages 32 are shown oneach side of the median plane AA, as the passages 32a, 32b, 32c, 32d,and 32:: each of which is formed to have its top wall 42 (Figs. 7, 8,and 9) directed at an angle to the cylinder bore of about 35 degrees,and its bottom wall 4-4 at an angle to the cylinder bore of about 20degrees, while the side walls. 45 converge toward the port end of thepassage (Fig. 2). Moreover and as may be observed from the developedview of the port system shown in Fig. 4,. the ports and passages withthe exception of the first passage 32a and its port l-tl, are preferablycanted in progressively greater degree, as with the end passage 32c andits port canted to the greatest extent. Consequently, the passages 32ato 32s as thus formed, constitute venturi-like nozzles which function toeffect in creased velocity of air delivery to the cylinder.

Referring again to Fig. 2, all of the air passages 32a to 32a aredirected as shown, such that the side walls 45 thereof he in planeswhich as indicated by the broken line projections 46, intersect themedian plane A-A in a zone B thereof extending longitudinally of thecylinder adjacent the cylinder wall at the side thereof opposite theexhaust port passages 27. It thus will appear also, that the wallelements 48 between adjacent passages on both sides of the median plane,lie in planes which intersect the median plane in the same zone B. Consequently, by the described formation and directioning of the air portpassages 32a to 32e on opposite sides of the median plane, thesepassages will serve to introduce jets of air through the ports 44} intothe cylinder and upwardly therein in a columnar stream along that sideof the cylinder which is opposite the side containing the exhaust portpassages. As before indicated, the air supply to the passages 32a to 32cis from the supply manifold 36 through the space or chamber 34 in. the

frame, the latter chamber being common to all of these passages, asshown in Fig. 2.

More particularly as to the sectional view of Fig. 2, the relativedirectioning of the side walls of the several port passages 32a to 32cat each side of the median plane A-A, is such as to cause the air jetsin admission to the cylinder, to flow along paths which in extendingupwardly in the cylinder toward the cylinder head end as determined bythe described inclination of the port passages, pass through a zone ofmutual intersection in their approach to the median plane A-A. Thus theseveral air jets or air streams are desirably united and connningled inthe zones or cylinder regions of such mutual intersection obtaining onopposite sides of the median plane, with all of the air streams thenforming a united columnar ilow upwardly in the cylinder along its sideopposite the exhaust port side. The foregoing is exemplified by themutual intersection of the broken lines 3 6 at each side of the medianplane, in their extension to intersection with the latter plane.Accordingly, the directioning of the port passage side walls 45 toattain this result, may be indicated by reference to the broken lines 46which as hereinbefore noted, are lines in the planes of the side walls.As shown by Fig. 2, the lines as in extension from the side walls 45 ofeach passage 32c, converge to intersection with the median plane A-A atthe point 2 thereof which is substantially at the cylinder wall surface,while those lines 46 in extension from the side walls of each portpassage 32d, converge to intersection with the median plane at the pointa thereof in the bore of the cylinder. Similarly, the lines lfi inextension from the side walls 55 of each passage 32c, converge tointersection with the median plane at the point 0 thereof in thecylinder bore. The line in extension from one side wall of each portpassage 32b, intersects the median plane at the point 0 thereof, whilethat line in extension from the opposite side wall of the passageintersects the median plane at a point b thereof in the cylinder bore.Finally, the line one side wall of each .port passage 32a, intersectsthe median plane at the point a thereof, while the line from theopposite side wall of the passage intersects the median plane at thepoint b thereof. While the above described intersection of the lines 46with the median plane, is that obtaining in the plane of the sectionalview of Fig. 2, the same character of intersection obtains between theplanes of the side walls 45 and the median plane, with intersectionappearing along lines in plane AA passing through the points e, d, c,and b, but with the lines of intersection at an angle to thelongitudinal cylinder axis in accordance with the degree of cant of theseveral'port passages and ports thereof, as such canted. condition isshown in Fig. 4.

With reference now to Figs. 3, 4, and S, the upper row of air portpassages 31 is provided by two sets orgroups of such passages, the setsbeing arranged on opposite sides of the median plane A-A and relativelyspaced apart by the arcuately long cylinder wall element 49 in themedian plane. Each set or group comprises according to the presentexample, three air passages 31a, 31b, and 310 terminating in air ports50 which as: appears from Fig. 4, are disposed above and approximatelyin line with the three intermediate ports 40 provided by the lower airpassages 32b. 32c, and 32d at the same side of the cylinder. Asexemplified in Fig. 8, each of the passages 31a, 31b, and 31c, is ofnozzle-form having the major extent of its top wall 52 inclined in thedirection of port 50, toward the head end of'the cylinder at an angle.to the cylinder bore of approximately '35 degrees, and its bottom wall53' similarly inclined over the: major portion thereof and atapproximately the. same angle. Moreover and as viewed in Fig. 3, thesidewalls 54 of these passages in' each, set, liein planes indicated bythe broken line projections 56, which intersect the median plane A--A inthe zone C thereof extending adjacent the cylinder wall at the sideopposite the exhaust port passages 27. Consequently, the wall elements57 between adjacent passages of each set, lie in planes which intersectthe median plane in the same zone. The sets of passages as so formed anddirected, serve to introduce jets of air through the ports into thecylinder and upwardly therein in a columnar stream along the side of thecylinder opposite the exhaust port side thereof.

In like manner and for the same reason as presented in connection withthe lower row of port 32a to 32e, the lines 56 in intersection with themedian plane as viewed in the sectional view of Fig. 3, may representthe character of mutual air jet intersection at opposite sides of themedian plane, as well as the passage wall directioning to obtain thisresult. As there appears, the lines 56 in extension from the side wallsor each port passage 31c, converge to intersection with the median planeat the point g thereof in the cylinder bore, while those lines from theside walls of each port passage 31b similarly converge to median planeintersection at the point h. One line 56 in extension from one Wall ofeach port passage 31a, intersects the median plane at the point h, whilethe line from the opposite wall of the passages intersects the medianplane at the point k thereof. Such is representative of the character ofintersection between the planes of the side walls 54 and the medianplane, and since the passages 31a, 31b, and 310 are not canted in theport arrangement according to Fig. 4, the intersections will appearalong lines in plane A-A passing through the points g, h, and k, whereinthe lines of intersection are parallel to the longitudinal axis of thecylinder.

As hereinbefore referred to, the frame is formed to provide separate airdelivery passages each leading to one of the sets of upper air passages31a, 31b, and 310 and having common communication with the inlet ends 58of the passages. Air under desired blower pressure in the supplymanifold 36, is supplied to each passage 35 under control of auni-directional valve device 38 associated with the passage and exposedin themanifold as shown in Fig. 1. The valve devices 38 may be of anysuitable type, adapted for permitting flow of air under pressure fromthe manifold through the valves into the passages 35, but preventingflow in the reverse direction through the valves.

6 Provided in the cylinder at the side thereof opposite the air portside, is a row of exhaust passages 27a, 27b, 27c, 27d, 27c, 27 and 27gdistributed in circumferentially spaced relation on opposite sides ofthe aforesaid median plane A--A and preferably symmetrically withrespect thereto, over approximately one-half the cylinder circumference.The intermediate group of exhaust passages 27b to 27 terminate inexhaust ports 60 in the inner wall surface of the cylinder. Thedimension of each port 60 in the longitudinal direction of the cylinderbore, is such that the port substantially spans the upper and lower rowsof air ports as this is illustrated in Fig. 4 showing one embodiment ofport arrangement. Moreover, port-formation by the passages 27b to 27 issuch that each port is of somewhat wedge-shape or tapered form infrontal view (Fig. 4), having its wide end uppermost, while the ports onopposite sides of the center port 27d disposed in the median plane A-Aand symmetrically related thereto, are cantedin the manner shown. Sincethe wide end of these ports is uppermost, the greater area thereof willbe uncovered first in the opening of the exhaust ports by the piston inthe exhaust cycle, whereby to afford a desirable exposure of a largetotal exhaust port area at the outset of cylinder exhaust scavenging, tofacilitate more rapid exhaust or so-called quick blowdown from thecylinder. The attainment of this result is considerably enhanced by theprovision herein, of the additional end exhaust passages 27a and 27geach of which provides an exhaust port 61 (Figs. 3, 4, and 7) disposedin the inner wall surface of the cylinder in a zone above or over theadjacent end port 40 of air passage 322. As will be observed from Fig.4, the dimension of each end exhaust port,61 in the longitudinaldirection of the cylinder bore, may be and preferably is less thanone-half the corresponding dimension of the ports 60 of the intermediategroup of exhaust port passages.

All of the exhaust passages 27a to 27g open into the common dischargechamber 28 formed by the engine frame, and the latter communicates withthe exhaust discharge manifold 30 (Fig. 1). Preferably, also, the exhaust port arrangement in the preferred embodiment, is such that the topmargins 62 of exhaust ports 60 and the top margins 64 of exhaust ports61 are disposed substantially in a common plane transversely through thecylinder, as this will be appreciated from Fig. 4. Moreover andparticularly in view of valve control of air delivery to the upper setsor groups of air ports 50, the latter may be arranged as shown in Fig.4, such that the top margins 65 thereof lie substantially in theaforesaid plane of the top exhaust port margins 62 and 64.

Additionally with regard to the exhaust passages, the sectional view ofFig. 6 illustrates the presently preferred inclination of the top andbottom walls of each of the exhaust passages 27b to 27]. As there shown,the passage top wall 66 is inclined toward its port 60 and in thedirection of the head end of the cylinder, by an angle of approximately75 degrees to the cylinder bore, while the bottom wall 68 is inclined inlike direction, by an angle of approximately degrees to the cylinderbore. On the other hand and as shown in Fig. 7, each end passage 27a and27g (27a being that shown) has its top wall 69 inclined in the samedirection and at the same angle of 75 degrees to the cylinder bore, andits bottom Wall 70 inclined in the same direction but at an angle ofabout 45 degrees to the cylinder bore.

Fig. 5 illustrates a modification as to the arrangement of exhaust andair ports, the chief difierences over the port arrangement shown in thedeveloped view of Fig. 4, residing in a reduction in the height of theintermediate air ports 72 in the lower row, and a similar reduction inthe height of the ports 73 in the upper row. This permits a compactingof the indicated sets of ports, in the longitudinal direction of thecylinder bore such that the top margins of the air ports in the upperrow are spaced from the transverse plane of the cylinder containing thetop margins of the intermediate exhaust ports '74 and end exhaust ports76. Consequently, piston opening of the exhaust ports in the exhaust orscavenging cycle, will occur ahead of piston opening of the upper row ofair ports, so that with this arrangement valve control of air deliveryto the upper ports 73 may be omitted without detracting unduly, from thescavenging and air charging effectiveness of the system.

In an engine having the presently preferred port system as nowdescribed, and operating on gaseous fuel with ignition attained in anysuitable manner, as by a pilot charge of liquid fuel, it will beobserved that as the piston moves to uncover the exhaust and air portsin the scavenging cycle, the large area ends of the exhaust ports areuncovered at the outset of the cycle to result in relatively rapidexhaust discharge with corresponding rapid reduction in cylinderpressure. Since at this point in the cycle, the upper row of air portsare uncovered to a like extent, some of the exhaust gases will passthrough these ports into the separate air delivery passages 35 towardthe closed valves 38. Because of this and for the purpose of controllingcylinder air charging as will appear presently, the passages 35' in theembodiment of the present invention are formed to have a total volumewhich is as small as is possible within practical design considerations.Consequently and because of the relatively rapid initial exhaustdischarge, these passages will be quickly evacuated of exhaust gases,with resultant decrease of pressure therein to a value below the airpressure in the supply manifold 36.

Air for cylinder scavenging than will be admitted past the valves. andthrough the upper row of air ports 55} into the cylinder. Such air isdirected by the ports in'the manner hereinbefore described, to pass asair jets, upwardly in the cylinder toward the head end thereof and alongthe side of the cylinder opposite the exhaust port side.

With further port-uncovering displacement of the piston, the remainderof the exhaust port area will be uncovered, together with uncovering ofthe lower row of air ports 4h. As the latter are opened, scavenging airenters the cylinder through these ports and is directed thereby to flowin jets upwardly in the cylinder in the side thereof opposite theexhaust port side. The air jets from both the upper and lower rows ofair ports, combine to form a columnar stream of scavenging air ofarcuate frontal form in the air port side of the cylinder, flowingupwardly in the cylinder, thence across the cylinder at the head end andin the combustion chamber space or" the cylinder head 12, and thendownwardly in the cylinder along the exhaust port side thereof, to theexhaust ports. Thus an etfectlve back flow or loop scavenging of theexhaust gases is obtained, the scavenging air column formed and directedto flow in the flow path described, displacing the exhaust gases andexpelling the same through the exhaust ports to ultimate dischargethrough the exhaust manifold 30. By the described directioning of theair port passages in both the upper and lower rows thereof, scavengingair delivery into the cylinder is such as to preclude short-circuitingflow of scavenging air across the cylinder from the air ports to theexhaust ports.

Upon reversal of piston displacement, cylinder scavenging is completedand charging of the cylinder with fresh combustion air takes place up topiston closure of the exhaust ports and the upper row of air ports. itis important to note here that the present improvements afford theprovision of a bottom row of air ports extending in an are overappreciably more than half the cylinder circumference, with each porthaving a relatively large port area which is greater than that of theindividual ports in the upper row as may be observed from Fig. 4. Thisdecidedly facilitates the attainment of an air and exhaust portrelationship such as that here provided, in which the ratio of total airport area to total exhaust port area obtaining during the main part ofthe cylinder air charging cycle, approaches the practical optimum ratiodetermined for efiicient and effective air charging in a two cycle highcompression engine running on gaseous fuel as here contemplated- Thefinal combustion air charge present in the cylinder following pistonclosure of the exhaust and air ports, is then more readily controlled asto volume and condition for proper mixture with the gaseous fuel,through the smaller area air ports of the upper row. it is to beobserved that by reason of the valve control of air supply through theupper ports and the port relation in which the top margins of theexhaust ports and the upper row of air ports are at about the samelevel, as in a common plane transversely through the cylinder, adesirable increased mean eflective scavenging and air charging pressureis obtained in the cylinder. Moreover and importantly to the attainmentof thorough mixture of air and gaseous fuel in proper combustionproportions, and the avoidance of gaseous fuel stratification as well asthe formation of cylinder pockets of rich, detonating mixtures of fueland air, the air directioning control afforded by the air ports andparticularly such control as is provided by the upper row of air portsprior to piston closure thereof, is most eliective to these ends. Thecolumnar movement of air in the cylinder in the indicated path about thecylinder center or core, not only prevents the establishment of richmixture pockets, but assures such distribution of air throughout thecylinder as to result in thorough commingling and diffusion of air andgaseous fuel to form a proper mixture for efficient combustion. Theresult of the foregoing is improved engine operation with increasedpower output.

sages as this may be observed from Fig. l. crown surface thus is adaptedfor cooperation with the port passages of both the upper and lower rows5 reef, to assist passage directioning of air jet admission to thecylinder and in so doing, to aid in preventing shortclrcuitlng ofscavenging air flow to the exhaust ports. the piston crown surface tillalso coacts with the exhaust port passages in exhaust discharge from thecylinder, by providing a desirable directioning of exhaust flow into theexhaust port passages.

While the described canting of a majority of both the air ports and theexhaust ports, as illustrated by Figs. 4 and 5, is highly desirableparticularly in respect to the air ports for assisting in obtaining theimproved directioning of air jet introduction to the cylinder, such portcanting is of importance to the minimizing of port-snagging of thepiston rings with resultant ring deterioration. Also, avoidance of ringdeterioration in this respect, is enhanced by the port arrangement nowprovided, wherein by reason of the addition of the smaller end exhaustports 61 (Fig. 4)

and 76 (Fig. 5), the circumferential cylinder are containing theremaining exhaust ports is somewhat less than otherwise would berequired.

The presently improved cylinder port arrangement as now described andillustrated, fully attains all of the hereinmentioned objects of theinvention, as well as other objects and advantages now apparent. It isdesired to point out in particular here, that the port system as hereindisclosed, so improves cylinder scavenging and air charging as toincrease the net power output of the engine, while affording anappreciable reduction in blower air supply over volumetric requirementsobtaining with port systems of heretofore known and prevailing forms.Consequently, with less air required in the present system, the airsupply blower may be of correspondingly reduced blower horsepowerrequirement, with resultant corresponding enhancement in the not poweroutput of the engine.

it is to be noted here that while the air ports in the upper and lowersets thereof, are shown to be distributed symmetrically with respect tothe median plane A-A, the ports of the upper set in particular, may bearranged in non-symmetrical relation to such plane in greater or lesserdegree as may be desired, or there may be a greater number of such portson one side of the plane than on the other side. Such modifications willserve to produce a twist or spiral effect in the columnar flow in thecylinder, such as to enhance the mixing of air and fuel.

Having now described and illustrated the present invention, what isclaimed:

1. In an internal combustion engine, a cylinder having exhaust passagesin the wall thereof terminating in exhaust ports in the inner surface ofthe cylinder wall, with the exhaust ports in circumferentially spacedrelation throughout substantially half the cylinder circumference, thetop margins of the exhaust ports lying in a common plane transversely ofthe cylinder and each end exhaust port having a dimension longitudinallyof the cylinder less than the corresponding dimension of the remainingexhaust ports, said cylinder providing a plurality of air passages inthe wall thereof and arranged such that certain of the air passagesterminate in a first row of air ports in the inner surface of thecylinder wall in clrcumferentially spaced relation over more than halfthe cylinder circumference, with the end ports of said row substantiallyunderlying said end exhaust ports, while the remaining air passagesterminate in a second row of air ports in the inner surface of thecylinder wall disposed abovethe first row The piston of air ports and incircumferentially spaced relation over less than half the cylindercircumference, all of said air passages being directed at an inclinationtoward one end of the cylinder, and the number of ports in said secondrow of air ports being less than the number of ports in said first rowof air ports.

2. In an internal combustionengine, a cylinder as defined by claim 1characterized further in that the said exhaust ports extendsymmetrically on opposite sides of a median plane through the center ofthe cylinder, and in that said certain air passages and said remainingair passages have the walls between adjacent passages thereof onbothsides of said median plane, disposed in planes intersecting saidmedian plane in a zone thereof remote from the exhaust ports.

3. In an internal combustion engine, a cylinder having passages inthewall thereof forming air ports arranged in rows one above another,the passages of each port row extending on opposite sides of a medianplane through the center of the cylinder and all of the passages beinginclined toward one end of the cylinder, said passages of each port rowhaving the walls between adjacent passages thereof on both sides of saidmedian plane, disposed in planes intersecting said median plane in azone thereof relatively adjacent one side of the cylinder wall, therebeing a wall element in said median plane at said one side of thecylinder wall, separating those air ports of one row which are nearestthe median plane and a second Wall element in the median planeseparating those air ports of another row which are nearest the medianplane, said one row of air ports being nearer said one end of thecylinder than said another row of air ports, and the first said wallelement being greater in extent circumferentially of the cylinder, thanthe said second wall element.

4. In an internal combustion engine, a cylinder having a plurality ofair passages in the cylinder wall providing upper and lower sets of airports in the inner ,wall surface of the cylinder, the air ports of eachset extending on opposite sides of a median plane through the center ofthe cylinder and the passages of each set of ports being inclined towardone end of the cylinder and having the walls between adjacent passagesthereof on both sides of said median plane, disposed in planesintersecting the median plane in a zone thereof relatively adjacent thecylinder wall, said cylinder further having a group of exhaust passagesin the cylinder wall providing a corresponding group of exhaust ports inthe inner wall surface of the cylinder, each exhaust port in said grouphaving a dimension longitudinally of the cylinder approximately thedistance as measured in the longitudinal direction of the cylinder,between the top margin of an air port in said upper set and the bottommargin of an air port in said lower set, and the cylinder having otherexhaust passages in the cylinder wall providing at least one additionalexhaust port in the inner surface of the cylinder Wall at each end ofsaid group of exhaust ports and in a position above an end air port ofsaid lower set of air ports.

5. In an internal combustion engine, a cylinder as defined by claim 4wherein the top margins of the said additional exhaust ports and the topmargins of the ports in said group of exhaust ports, are substantiallyin a common plane transversely through the cylinder.

6. In an internal combustion engine, an engine frame, a cylindersupported in the frame, said cylinder having a plurality of air passagesin the cylinder wall substantially at one side of the cylinder, certainof said passages terminating in a first set of cylinder air portsarranged in a row extending on opposite sides of a median plane throughthe cylinder center, others of said air passages terminating in a secondset of cylinder air ports arranged in a row at one side of said medianplane and above the first mentioned row of air ports, and the remainderof said air passages terminating in a third set of cylinder air portsarranged in a row at the opposite side of said median plane and abovethe first mentioned row of air ports, said second and third sets of airports having the end] ports thereof nearest said median plane spacedapart by a distance materially greater than the distance separating theadjacent pair of ports of said first set nearest the median plane; saidcylinder providing a plurality of exhaust passages in the cylinder wallat the opposite side of the cylinder, the exhaust passages terminatingin cylinder exhaust ports arranged in a row extending on opposite sidesof said median plane, with the exhaust port at each end of said rowdisposed substantially above an end air port of said first set of airports; all of said plurality of air passages being inclined toward oneend of the cylinder, the passages of said first set of air ports havingthe walls between adjacent passages thereof on both sides of said medianplane, disposed in planes intersecting the median plane in. a zonethereof remote from the exhaust ports, and the passages of said secondand third set of air ports having the walls between adjacent passagesthereof disposed in planes intersecting said median plane in said zonethereof; said frame providing an air delivery passage in commoncommunication with the air passages of said second set of air ports anda separate air delivery passage in common communication with the airpassages of said third set of air ports, and a unidirectional valve incontrol of each air delivery passage.

7. In an internal combustion engine, an engine frame, a cylindersupported in the frame, the cylinder having exhaust port passagesproviding a row of exhaust ports in the cylinder wall, the exhaust portrow being arranged symmetrically with respect to a median plane throughthe center of the cylinder and extending over substantially half thecylinder circumference, the top margins of said ports lying in a commonplane transversely of the cylinder and the end port at each end of therow having a port height longitudinally of the cylinder, substantiallyless than the port height of the remaining exhaust ports, the cylinderfurther having a first set of air port passages providing a row of airports in the cylinder wall arranged substantially symmetrically relativeto said median plane and extending over greater than half the cylindercircumference, with the air port at each end of the row substantiallyunderlying the end exhaust port at the corresponding end of the exhaustport row, and other sets of air port passages provid ing additional airports above the first said row of air ports, said additional air portsbeing arranged in separate, spaced apart rows with one such row on eachside of said median plane, said other sets of air port passages beinginclined toward one end of the cylinder and directed toward the side ofthe cylinder opposite the side thereof containing said exhaust ports,and said engine frame providing sepa rate air delivery passages eachcommunicating with a set of said other sets of air port passages.

8. In an internal combustion engine, the subject matter according toclaim 7, wherein the said first set of air port passages are inclinedtoward one end of the cylinder and are directed substantially toward theside of the cylinder opposite the side thereof containing the saidexhaust ports.

9. In an internal combustion engine, an engine frame, a cylindersupported in the frame, the cylinder having a plurality of port passagesterminating in main exhaust ports, auxiliary exhaust ports and air portsin the cylinder wall, all of said ports being confined substantially toa single cylinder port belt of a width longitudinally of the cylinder,substantially commensurate with the height of the main exhaust ports,said main exhaust ports being arranged in a row extending symmetricallywith respect to a median plane through the center of the cylinder, saidauxiliary exhaust ports being arranged to provide one such port at eachend of said row ofmain exhaust ports, the top margins of the main andauxiliary exhaust ports lying in a common plane transversely of thecylinder and the height of each auxiliary exhaust port being less thanthe height of the main exhaust ports, certain of said air ports beingarranged in a first row extending symmetrically with respect to saidmedian plane and having the air port at each end of the rowsubstantially underlying the auxiliary exhaust port at the correspondingend of the exhaust port row, the remaining air ports being above saidfirst row of air ports and arranged to provide separate, spaced apartair port rows with one such row on each side of said median plane, andthe port passages terminating in said remaining air ports being inclinedtoward one end of the cylinder and directed toward the side of thecylinder opposite the side thereof containing said main exhaust ports.

10. Inan internal combustion engine, the subject matter according toclaim 9 wherein the port passages terminating in the air ports of thesaid first row, are inclined toward one end of the cylinder and aredirected substantially toward the side of the cylinder opposite the sidethereof containing the said main exhaust ports.

11. In an internal combustion engine, the subject matter according toclaim 9 wherein the said engine frame provides separate air deliverypassages each communicating with the port passages of one of the saidseparate, spaced apart air port rows.

References Cited in the file of this patent UNITED STATES PATENTS1,689,834 Kreissle Oct. 30, 1928 1,973,859 Thomann Sept. 18, 19342,038,271 Curtis Apr. 21, 1936 2,044,552 Walti June 16, 1936 2,128,855Schenker Aug. 30, 1938 2,187,287 Tobler Jan. 16, 1940 2,218,202Lieberherr Oct. 15, 1940 2,393,342 Schneider Jan. 22, 1946 FOREIGNPATENTS 146,936 Switzerland July 16, 1931 304,181 Italy Dec. 29, 1932Great Britain July 30, 1947

